The present invention relates to a nonmagnetic material particle dispersed ferromagnetic material sputtering target, and in particular relates to a nonmagnetic material particle dispersed ferromagnetic material sputtering target which realizes, in the formation of a film by sputtering, stable direct current (DC) sputtering and optimal deposition speed, minimal arcing during the sputtering, reduction in the particles (dust) and nodules caused by such arcing, high density, minimal variation in quality, and improvement of mass productivity.
In the field of magnetic recording, technology has been developed for improving the magnetic property by causing a nonmagnetic material to coexist in a magnetic body thin film. Some of the examples are technology for improving the soft magnetic property such as magnetic permeability by causing fine particles of the nonmagnetic material to exist in the magnetic material thin film, and technology for improving various properties as a magnetic recording medium such as coercitivity by using the nonmagnetic material to block or weaken the magnetic interaction between the fine metallic particles in the magnetic body thin film material.
Although this kind of thin film material is prepared based on normal sputtering, it is necessary to simultaneously sputter nonmagnetic materials with insulation property or high resistance and ferromagnetic materials with low resistance or composed from metals.
This sputtering method makes a positive electrode substrate and a negative electrode target face each other, and generates an electric field by applying high voltage or radio frequency between the substrate and the target under an inert gas atmosphere.
Here, the sputtering method employs a fundamental principle where inert gas is ionized, plasma formed from electrons and positive ions is formed, and the positive ions in this plasma collide with the target (negative electrode) surface. The extruded atoms adhere to the opposing substrate surface, wherein the film is formed.
As the general sputtering method, the RF (radio frequency) sputtering method or the DC (direct current) sputtering method may be used. However, in order to sputter materials with significantly different resistance simultaneously, the RF sputtering method that is capable of sputtering an insulator is often used.
Nevertheless, not only is the RF (radio frequency) sputtering device expensive, it possesses numerous drawbacks such as inferior sputtering efficiency, large power consumption, complex control and slow deposition speed. If high power is applied to increase the deposition speed, the substrate temperature will rise, and there is a problem in that this will cause deterioration in the substrate and deposition material.
Meanwhile, since the DC sputtering method has low power consumption, is capable of high speed deposition and is inexpensive in comparison to the RF sputtering method, it is superior in mass productivity. In addition, it is generally said that the DC sputtering method is able to produce high-quality films since the influence of the plasma on the substrate is small.
Accordingly, a sputtering target for simultaneous sputtering a nonmagnetic material and a ferromagnetic material is also devised so that it can be used in DC sputtering as much as possible. When adopting the DC sputtering method, the target itself needs to possess conductive property.
Even if the target possesses conductive property, if such target contains large amounts of nonconductive property material such as oxides and silicides, deposition based on DC sputtering will become difficult since the bulk resistance of the target will increase.
Thus, a sputtering target has been devised to have a structure in which a nonmagnetic material such as oxides is finely and spherically dispersed therein. Nevertheless, even with this kind of devisal, there is a problem in that large amounts of particles are generated.
Some background art are introduced below. As one example, proposed is a method of performing mechanical ironing to alloy powder having an alloy phase prepared with the rapid solidification method, and ceramic phase powder (refer to Patent Document 1). According to this methods it is possible to obtain a sputtering target for use in a magnetic recording medium by preparing alloy powder in which ceramic phase powder is evenly dispersed in the alloy powder, and thereafter molding this by way of hot pressing.
As another example, proposed is Co-based alloy containing a silica phase in which the average width there sought with the line segment method is in the range of 0.5 to 5 μm, as well as Cr and Pt phases (refer to Patent Document 2). The silica powder in this case is obtained with a special method of high temperature flame hydrolysis deposition.
Nevertheless, with respect to the materials obtained with the foregoing methods, in the case of the former (first example), the object is simply forming the particles uniformly as much as possible, and in the case of the latter (second example), although a target structure distributed in a web shape is obtained, the existence of coarse grains can be observed in certain locations. Based on these types of methods, it is assumed that particles will increase enormously upon forming a film based on sputtering as described later, which will be unfit as a target material.    [Patent Document 1] Japanese Patent Laid-Open Publication No. H10-88333    [Patent Document 2] Japanese Patent Laid-Open Publication No. 2004-339586